Boss Dm-2 LED on but no guitar signal

[Martin101]

Hi all

I recently purchased a Boss Dm-2 on ebay . I got it today but when I connect it to my amp and guitar there is no signal, wheather the LED light is on or not. I'm using it with a 9v battery. What's going on. The amp acts like there is nothing connected to it.

[Brad1]

Make sure the battery is new and running full charge. A lot of Boss pedals will light up, but pass no effect, if the battery is just below what it needs, but high enough to light the LED. My DM2 has done the same thing.

If it's not that, then...?

Brad1

[Martin101]

Thanks for the info.

I put in a fresh 9v battery and it still does the same thing.

When I put the amp volume higher I hear a hiss.

[Jazz P Bass]

Well, it sounds like you bought a dud.
These DM-2 pedals are a bit complicated, in the circuitry.
Boss used selected IC's (whatever that means) which, not knowing what was selected for, may make it tough to repair.
If you have experience at repairing pedals, it is still going to be a tough nut.
I have included the schematic.

[Martin101]

Thanks for the info.

I've contacted the seller, he's been helpful but he claims it worked when he shipped it.

I don't know anything about the insides of a pedal so either I'll try to get a refund or see if someone in my neck of the woods here can repair it. There is just no signal when the guitar is plugged into the amp, all I hear is a hiss.

I hope I didn't break it, the worst I did was dasiy chained it to other Boss pedals when I first tried it and it did the same thing.

I carefully opened it up, it looks like one of the wires is loose.

[Mark Hammer]

The fact that nothing is coming through in either bypass or effect mode suggests a fractured wire or something amiss with the jack more than anything. That is, the entire circuit board may be functioning 100% flawlessly (as indicated by the seller), but getting what is on the circuit board to the output (or alternatively, from the input jack to the circuit board), may be the problem.

If it was the case that you had normal bypass signal, but got no effect when in effect mode, then the obvious suspect would be either a bum switching FET (which happens), or the bias trimpot for the delay chip moving position (which also happens). But since you say there is no signal whatsoever, your first task is to gently take the back off, dislodge the board, and check for any broken wires.

If you DO find one or more, then it should be possible to find "gutshots" of the pedal online, via a Google image search, that can help you identify where the wire goes to (or comes from). Happily, the wires are color coded.

[Martin101]

I added pics of the inside, there is a wire loose.

[Mark Hammer]

Looking here - Boss DM-2 Delay Guitar Pedal Schematic Diagram - I see that a) that brown wire is connection #2 on the board, and b) it is the wire from the input jack to the board. No wonder you didn't hear anything at all.

Strip a bit of the insulation off the wire, tin the exposed wire, and solder it in place. That should restore full functioning.

That wasn't so hard, now, was it? Gotta love happy endings.

[Martin101]

wow everyone. Thanks so much!